<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
let a = 10;//弱类型
console.log(a);
const b = 20;
console.log(b);
alert(typeof 10);//number
alert(typeof 2.5);//number
alert(typeof true);//boolean
alert(typeof 'hello world');//string
alert(typeof undefined);//undefined
alert(typeof null);//object

</script>
<script>
    //模版字符串
    let name = '张三';
    let age = 18;
    let sex = '男';
    let info = `我是${name},我今年${age}岁,我是${sex}`;//反引号
    console.log(info);
    alert(info);

</script>
</body>
</html>